r-Selected benthic foraminifera with associated bacterial colonies in Upper Pleistocene sediments of the Ross Sea (Antarctica): implications for calcium carbonate preservation

Investigations on foraminifera from Upper Pleistocene-Holocene sediments co red in the continental slope of the western Ross Sea (2383 m water depth) r evealed that the record of calcareous assemblages was restricted to a limit ed time interval (approximately 6 kyr) and characterized by a dominance of phytodetritus-exploiting taxa, such as Alabaminella weddellensis and Episto minella exigua. Rod-shaped calcified, fossil bacteria infest the partially dissolved calcareous foraminiferal surfaces, either as clusters or as isola ted cells, suggesting that significant changes (from under-to oversaturated conditions with respect to calcium carbonate) in the chemistry of the seaw ater developed before the final burial of the foraminiferal tests. We postu late that bacterial activity on a microenvironmental scale (interface and p ore water) in the sea floor could influence pore water conditions in such a way as to preserve carbonate in deep marine regions where environmental co nditions usually prevent the establishment of carbonate secreting communiti es. (C) 1999 Elsevier Science B.V. All rights reserved.